The present invention relates to a lifting apparatus and a more particularly to a lifting apparatus having a lift platform movable by a pneumatically inflatable spring, air bag, balloon, cushion, hydraulic cylinder, air cylinder or air bellows.
Lift platforms are used to raise and lower various items. In some cases the lift platform is used to lift a person(s) to a level which makes it easier for the person to perform his or her tasks. In other applications a part(s) or other object is placed on the lift platform and the lift platform raises or lowers the height of the part in relation to the operator. By moving the operator(s) or the part(s) to more ergonomic work locations, the efficiency of the operator is increased, the time to complete a given task is generally reduced, and operator's health is maintained by minimizing stress and strain of the human body during the job task.
The prior art shows many differently configured hydraulic and pneumatic lift mechanisms. One such lift is shown in U.S. Pat. No. 3,994,474 and includes two parallel-configured sides plates moved by an air spring (air bag). U.S. Pat. No. 6,286,812 shows another lifting platform which uses a scissors-type of linkage which is movable by an inflatable bag.
The present invention is configured to move the lift platform in an essentially parallel manner relative to the base without using scissors or folding linkages (as shown in the prior art) while employing a lift mechanism movable in a generally upward direction to minimize the force needed to lift an object, part or person. Experience has shown this approach also reduces the cost of the lift apparatus in relation to scissor lifting mechanism. The present invention utilizes a one-to-one direct, vertical lift ratio which provides an improved system. In the context of an air spring a one-to-one direct lifting ratio relates to the way in which the air spring dynamic load force vectors are applied during the lifting cycle such that for every unit of measure the lift platform raises during the lifting cycle the air spring travels the same unit of measure. The vertical loads are transferred directly through the air spring to the floor level or support structure.
One of the advantages of the present invention is the lift (and its components) can be lowered to an very low profile (and subsequently raised) which accommodates a wider range of operator statures to enable, where desired, to place the platform so the work piece is in the neutral posture range of the human body commonly referred to as the knuckle-to-elbow range.
One embodiment of the present invention uses a lift mechanism in the form of a parallelogram linkage which is moved by an air spring. The top of the air spring is fixed to the underside of the lift platform and by virtue of the flexibility of the air spring and the parallelism of the linkage, the air spring is able to follow the longitudinal movement of the platform.
It is an object of the present invention to provide to a lift platform with improved ergonomically characteristics which permit an increase in operator efficiency and a decrease in operator injury.
Accordingly the invention comprises: a lifting apparatus comprising: one of a mobile or stationary base; a lift platform having a geometric first center, the lift platform movable relative to the base from a lowered position to an upper position; a linkage or linkage mechanism interconnecting the base and the lift platform for guiding the lift platform to remain in a generally mutually parallel relationship with the base. The base, lift platform and linkage are configured so that when the lift platform in its lowered position the center of the lift platform intersects the base at a first point and with the lift platform in its upper position the center intersects the base at a second point which is longitudinally off-set from the first point. The lifting apparatus also includes a fluid (in general liquid or pneumatic) spring operatively mounted between the lift platform and the base, for controllably lifting and lowering the lift platform. Single and multi-chambered air springs are described as well as two, three and four bar linkage mechanisms and various control mechanisms are provided to control the movement of the lift platform.
Many other objects and purposes of the invention will be clear from the following detailed description of the drawings.